Analytical Chemistry problem solving

For analysis of a cola drink 1.000 cm3 of the drink was treated with 50 microlitres (i.e. 0.050 cm3) of a standard solution containing 1.11 g dm-3 of caffeine-D3 as the internal standard in methanol. The combined solution was passed through a solid-phase microextraction (SPME) column that retains caffeine. Polar solutes were washed off with H2O. The caffeine was washed off with dichloromethane and the solvent was evaporated to leave a dry residue. This material was dissolved in 50 microlitres (i.e. 0.050 cm3) of methanol for GC-MS analysis. The peak area for the internal standard was 1144, while the peak area of what corresponded to caffeine was 1733. Estimate the concentration of caffeine in the original cola drink. (NB: You can assume that the response factor for the detector was 1.000).